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  • Publication
    Accès libre
    Glasshouse vs field experiments: do they yield ecologically similar results for assessing N impacts on peat mosses?
    (2012)
    Limpens, J.
    ;
    Granath, G.
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    Aerts, R.
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    Heijmans, M. M. P. D.
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    Sheppard, L. J.
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    Bragazza, L.
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    Williams, B. L.
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    Rydin, H.
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    Bubier, J.
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    Moore, T.
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    Rochefort, L.
    ;
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    Buttler, A.
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    van den Berg, L. J. L.
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    Gunnarsson, U.
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    Francez, A. -J.
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    Gerdol, R.
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    Thormann, M.
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    Grosvernier, P.
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    Wiedermann, M. M.
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    Nilsson, M. B.
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    Hoosbeek, M. R.
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    Bayley, S.
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    Nordbakken, J. -F.
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    Paulissen, M. P. C. P.
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    Hotes, S.
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    Breeuwer, A.
    ;
    Ilomets, M.
    ;
    Tomassen, H. B. M.
    ;
    Leith, I.
    ;
    Xu, B.

    • Peat bogs have accumulated more atmospheric carbon (C) than any other terrestrial ecosystem today. Most of this C is associated with peat moss (Sphagnum) litter. Atmospheric nitrogen (N) deposition can decrease Sphagnum production, compromising the C sequestration capacity of peat bogs. The mechanisms underlying the reduced production are uncertain, necessitating multifactorial experiments.
    • We investigated whether glasshouse experiments are reliable proxies for field experiments for assessing interactions between N deposition and environment as controls on Sphagnum N concentration and production. We performed a meta-analysis over 115 glasshouse experiments and 107 field experiments.
    • We found that glasshouse and field experiments gave similar qualitative and quantitative estimates of changes in Sphagnum N concentration in response to N application. However, glasshouse-based estimates of changes in production – even qualitative assessments – diverged from field experiments owing to a stronger N effect on production response in absence of vascular plants in the glasshouse, and a weaker N effect on production response in presence of vascular plants compared to field experiments.
    • Thus, although we need glasshouse experiments to study how interacting environmental factors affect the response of Sphagnum to increased N deposition, we need field experiments to properly quantify these effects.
  • Publication
    Métadonnées seulement
    Climatic modifiers of the response to nitrogen deposition in peat-forming Sphagnum mosses: a meta-analysis
    (2011)
    Limpens, J.
    ;
    Granath, G.
    ;
    Gunnarsson, U.
    ;
    Aerts, R.
    ;
    Bayley, S.
    ;
    Bragazza, Luca
    ;
    Bubier, J.
    ;
    Buttler, Alexandre
    ;
    van den Berg, L. J. L.
    ;
    Francez, Andre-Jean
    ;
    Gerdol, R.
    ;
    Grosvernier, Philippe
    ;
    Heijmans, M. M. P. D.
    ;
    Hoosbeek, M. R.
    ;
    Hotes, S.
    ;
    Ilomets, M.
    ;
    Leith, I.
    ;
    ;
    Moore, T.
    ;
    Nilsson, Mats B.
    ;
    Nordbakken, J. F.
    ;
    Rochefort, L.
    ;
    Rydin, H.
    ;
    Sheppard, L. J.
    ;
    Thormann, M.
    ;
    Wiedermann, M. M.
    ;
    Williams, B. L.
    ;
    Xu, B.
    Peatlands in the northern hemisphere have accumulated more atmospheric carbon (C) during the Holocene than any other terrestrial ecosystem, making peatlands long-term C sinks of global importance. Projected increases in nitrogen (N) deposition and temperature make future accumulation rates uncertain. Here, we assessed the impact of N deposition on peatland C sequestration potential by investigating the effects of experimental N addition on Sphagnum moss. We employed meta-regressions to the results of 107 field experiments, accounting for sampling dependence in the data. We found that high N loading (comprising N application rate, experiment duration, background N deposition) depressed Sphagnum production relative to untreated controls. The interactive effects of presence of competitive vascular plants and high tissue N concentrations indicated intensified biotic interactions and altered nutrient stochiometry as mechanisms underlying the detrimental N effects. Importantly, a higher summer temperature (mean for July) and increased annual precipitation intensified the negative effects of N. The temperature effect was comparable to an experimental application of almost 4 g N m(-2) yr(-1) for each 1 degrees C increase. Our results indicate that current rates of N deposition in a warmer environment will strongly inhibit C sequestration by Sphagnum-dominated vegetation.